The invention described herein relates generally to brazing. More specifically, the invention relates to a method of brazing.
Armature stator bars in large generators are usually liquid cooled and contain a combination of individually insulated conductors, comprising both solid and hollow strands. The hollow strands are used to transmit liquid coolant, as well as electric current through the length of the armature stator bar. A header, including generator connection rings, must be leak resistant and capable of conducting electric current. This assembly is affixed to each end of each armature stator bar.
The headers and connection rings presently in service in generators serve as electrical connections between the stator bars or phase rings of the armature circuit and are also the sealed enclosure for transferring the liquid coolant to and from the stator bars. Conventional headers and connection rings are normally brazed to both the hollow and solid strands at each end of the stator bars. Thus, the liquid coolant is in direct contact with the brazed joints, which can result in liquid coolant leaks due to braze joint corrosion or braze joint imperfections. Ensuing leaks of liquid coolant can damage the armature insulation and result in costly maintenance outages.
Thus, there is a need for an improved brazing method that improves joint quality and reduces the leak problem.